The present invention generally relates to low voltage current sources and current mirrors, and more particularly relates to low voltage current sources and current mirrors that are highly stable under varying external loads.
In the past, the required power supply voltage of semiconductor circuits dropped constantly as semiconductor technology progressed. This power supply reduction has been required for fundamental device and technology reasons, as well as for higher level circuit and system requirements. The drop in the required power supply voltage for analog circuits has lagged the drop in the power supply voltage for digital circuits, and solutions have been sought to fill this gap between the two categories of circuits to make both analog and digital circuits operate at a similar power supply, particularly in those cases where both analog and digital circuits are present on the same semiconductor integrated circuit.
Future generation technologies and applications raise complex challenges for a further reduction in the power supply voltage. The requirements with respect to fundamental device physics on one hand, and fundamental circuit and system restrictions on the other hand, oppose each other when the ultimate possible limits for power supply voltage reduction for next generation technologies are pursued. The principal reason that generates this contradiction is that this evaluation is made with reference to the present state of the art. In addition, system-on-a-chip (SOC) total integration circuitry generates additional challenges in achieving the power supply voltage reduction goals for the next generation technologies and applications. According to SOC requirements, analog, RF, digital, and memory blocks must all coexist on-chip while operating at the same power supply voltage and interacting minimally (such as generating minimal noise and being highly immune to the received noise). To overcome these challenges, novel devices and/or a novel circuit/system design approach must be developed.